U.S. patent application number 10/281554 was filed with the patent office on 2003-02-27 for strain relief mechanism for a plasma arc torch.
Invention is credited to Eickhoff, Stephen T., Morris, Ronald E..
Application Number | 20030038119 10/281554 |
Document ID | / |
Family ID | 25305780 |
Filed Date | 2003-02-27 |
United States Patent
Application |
20030038119 |
Kind Code |
A1 |
Eickhoff, Stephen T. ; et
al. |
February 27, 2003 |
Strain relief mechanism for a plasma arc torch
Abstract
The present invention relates to a strain relief mechanism for a
plasma arc torch. In particular, the invention relates to a strain
relief system including a positive axial restraint component for
restraining axial movement of a lead relative to a housing and a
positive rotational restraint component for restraining rotational
movement of the lead relative to the housing, wherein the positive
axial restraint component and the positive rotational restraint
component are independent components arranged in a spaced
relationship relative to each other.
Inventors: |
Eickhoff, Stephen T.;
(Hanover, NH) ; Morris, Ronald E.; (New London,
NH) |
Correspondence
Address: |
TESTA, HURWITZ & THIBEAULT, LLP
HIGH STREET TOWER
125 HIGH STREET
BOSTON
MA
02110
US
|
Family ID: |
25305780 |
Appl. No.: |
10/281554 |
Filed: |
October 28, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10281554 |
Oct 28, 2002 |
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09849446 |
May 4, 2001 |
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6472631 |
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Current U.S.
Class: |
219/121.39 |
Current CPC
Class: |
B23K 9/32 20130101; B23K
10/00 20130101; H05H 1/34 20130101; B23K 9/323 20130101 |
Class at
Publication: |
219/121.39 |
International
Class: |
B23K 010/00 |
Claims
What is claimed is:
1. A strain relief system for restraining a lead relative to a
housing, the system comprising: (a) a positive axial restraint
component for restraining axial movement of the lead relative to
the housing; and (b) a positive rotational restraint component for
restraining rotational movement of the lead relative to the
housing, wherein the positive axial restraint component and the
positive rotational restraint component are independent components
arranged in a spaced relationship relative to each other.
2. The strain relief system of claim 1 wherein the positive axial
restraint component and the positive rotational restraint component
are arranged in a spaced relationship relative to a longitudinal
axis of the lead.
3. The strain relief system of claim 1 wherein the positive axial
restraint component and the positive rotational restraint component
are configured so that both are engaged simultaneously when the
lead is connected to the housing.
4. The strain relief system of claim 1 wherein the positive axial
restraint component comprises a quick disconnect connector.
5. The strain relief system of claim 4 wherein the positive axial
restraint component further comprises a quick disconnect connector
receptacle.
6. The strain relief system of claim 1 wherein the positive
rotational restraint component comprises a shaped boot attached to
the lead.
7. The strain relief system of claim 6 wherein the positive
rotational restraint component further comprises a mating
receptacle in the housing for accepting the shaped boot.
8. The strain relief system of claim 1 wherein the positive axial
restraint component comprises a quick disconnect connector and the
positive rotational restraint component comprises a shaped boot
attached to the lead.
9. The strain relief system of claim 1 wherein the lead comprises a
fluid line and at least one electrical conductor.
10. The strain relief system of claim 9 further comprising an
electrical connection connecting the at least one electrical
conductor with a mating connector in the housing.
11. The strain relief system of claim 9 wherein the fluid line is
generally centrally disposed in the lead and the at least one
electrical conductor is disposed radially outwardly therefrom.
12. A plasma arc torch for piercing or cutting a workpiece, the
torch comprising: a torch body; a power supply; a lead comprising a
first end connected to the torch body and a second end; and a
strain relief system to couple the second end of the lead to the
power supply, wherein the strain relief system comprises: (a) a
positive axial restraint component for restraining axial movement
of the lead relative to the power supply; and (b) a positive
rotational restraint component for restraining rotational movement
of the lead relative to the power supply, wherein the positive
axial restraint component and the positive rotational restraint
component are independent components arranged in a spaced
relationship relative to each other.
13. The torch of claim 12 wherein the positive axial restraint
component and the positive rotational restraint component are
arranged in a spaced relationship relative to a longitudinal axis
of the lead.
14. The torch of claim 12 wherein the positive axial restraint
component and the positive rotational restraint component are
configured so that both are engaged simultaneously when the lead is
connected to the power supply.
15. The torch of claim 12 wherein the positive axial restraint
component comprises a quick disconnect connector.
16. The torch of claim 15 wherein the positive axial restraint
component further comprises a quick disconnect connector
receptacle.
17. The torch of claim 12 wherein the positive rotational restraint
component comprises a shaped boot attached to the lead.
18. The torch of claim 17 wherein the positive rotational restraint
component further comprises a mating receptacle in the power supply
for accepting the shaped boot.
19. The torch of claim 12 wherein the positive axial restraint
component comprises a quick disconnect connector and the positive
rotational restraint component comprises a shaped boot attached to
the lead.
20. The torch of claim 12 wherein the lead comprises a fluid line
and at least one electrical conductor.
21. The torch of claim 20 further comprising an electrical
connection connecting the at least one electrical conductor with a
mating connector in the power supply.
22. The torch of claim 20 wherein the fluid line is generally
centrally disposed in the lead and the at least one electrical
conductor is disposed radially outwardly therefrom.
23. A method for restraining a lead relative to a housing, the
method comprising the steps of: (a) providing a positive axial
restraint component for restraining axial movement of the lead
relative to the housing; (b) providing a positive rotational
restraint component for restraining rotational movement of the lead
relative to the housing, wherein the positive axial restraint
component and the positive rotational restraint component are
independent components arranged in a spaced relationship relative
to each other; and (c) connecting the lead to the housing.
24. The method of claim 23 wherein the positive axial restraint
component and the positive rotational restraint component are
arranged in a spaced relationship relative to a longitudinal axis
of the lead.
25. The method of claim 23 wherein the positive axial restraint
component and the positive rotational restraint component are
configured so that both are engaged simultaneously when the lead is
connected to the housing.
26. The method of claim 23 wherein the positive axial restraint
component comprises a quick disconnect connector.
27. The method of claim 26 wherein the positive axial restraint
component further comprises a quick disconnect connector
receptacle.
28. The method of claim 23 wherein the positive rotational
restraint component comprises a shaped boot attached to the
lead.
29. The method of claim 28 wherein the positive rotational
restraint component further comprises a mating receptacle in the
housing for accepting the shaped boot.
30. The method of claim 23 wherein the lead comprises a fluid line
and at least one electrical conductor.
31. The method of claim 30 wherein the fluid line is generally
centrally disposed in the lead and the at least one electrical
conductor is disposed radially outwardly therefrom.
32. The method of claim 30 wherein the method further comprises the
step of: (d) connecting the at least one electrical conductor to a
mating connector in the housing.
33. A method for restraining a lead relative to a power supply for
a plasma arc torch, the method comprising the steps of: (a)
providing a positive axial restraint component for restraining
axial movement of the lead relative to the power supply for the
plasma arc torch and a positive rotational restraint component for
restraining rotational movement of the lead relative to the power
supply for the plasma arc torch, wherein the positive axial
restraint component and the positive rotational restraint component
are independent components; (b) arranging the positive axial
restraint component and the positive rotational restraint component
in a spaced relationship relative to each other along a
longitudinal axis of the lead; and (c) connecting the lead to the
power supply for the plasma arc torch.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a strain relief mechanism for a
tool. In particular, the invention relates to a strain relief
mechanism for a plasma arc torch which includes a positive axial
restraint component and a positive rotational restraint
component.
BACKGROUND OF THE INVENTION
[0002] Plasma arc torches are widely used in the cutting or marking
of metallic materials. A plasma torch generally includes an
electrode and a nozzle having a central exit orifice mounted within
a torch body, electrical connections, passages for cooling and arc
control fluids, a swirl ring to control fluid flow patterns in the
plasma chamber formed between the electrode and nozzle, and a power
supply. The torch produces a plasma arc, which is a constricted
ionized jet of a gas with high temperature and high momentum. Gases
used in the torch can be non-reactive (e.g. argon or nitrogen), or
reactive (e.g. oxygen or air).
[0003] In operation, a pilot arc is first generated between the
electrode (cathode) and the nozzle (anode). Generation of the pilot
arc may be by means of a high frequency, high voltage signal
coupled to a DC power supply and the torch or any of a variety of
contact starting methods.
[0004] One known configuration of a plasma arc torch includes one
or more leads connecting the torch to the power supply to provide
the torch with electrical current and gas. The connection of the
lead(s) to the power supply must be rugged to handle the strain
placed on the lead as it is manipulated in order to place the
plasma arc torch in a position to cut or mark a workpiece. While
most operators of hand-held systems use the plasma arc torch, lead
and power supply properly, some operators have used the lead for
purposes not intended by the manufacturer (e.g. stepping on the
lead(s) or even pulling the lead(s) to drag the power supply to a
new location).
[0005] The lead(s) used to connect the torch to the power supply
can be a single integral lead having a gas hose located in the
middle of the lead and electrical conductors and fillers arranged
symmetrically around the gas hose. A jacket material is extruded
over the gas hose, electrical conductors and fillers. A strain
relief mechanism can be attached to the jacket to handle loads
applied to the lead. The jacket, gas hose, electrical conductors
and fillers are anchored together over a barb-type fitting. A
clamp, which acts as the strain relief mechanism, is applied to
grab and hold the jacket to prevent relative axial motion (or
twisting) of the lead components. The stress through the lead is
absorbed by the clamp and transferred to the chassis of the power
supply through a mechanical connection.
[0006] One example of an integral lead with a clamp which prevents
axial motion or twisting of lead components is found in the lead
used in the PMX900/PAC 125 plasma arc torch system manufactured by
Hypertherm, Inc. The lead used in this plasma arc torch system is
connected to the power supply by a threaded quick disconnect
connector. A quick disconnect connector is advantageous in that it
simplifies torch removal but is expensive to make. Another example
of an integral lead with a clamp for preventing axial motion (or
twisting) of lead components can be found in the lead used in the
PMX600/PAC123 plasma arc torch system manufactured by Hypertherm,
Inc. In this system, stress is absorbed by the chassis of the power
supply through a tool-tightened nut. A tool-tightened nut is
advantageous in that it is inexpensive, but the tool-tightened nut
requires the use of a tool. The use of a tool can be time
consuming, and the tool can be easily misplaced.
[0007] It is therefore an object of the present invention to
provide an improved and inexpensive axial and rotational strain
relief mechanism for connecting a lead to a plasma arc torch power
supply.
SUMMARY OF THE INVENTION
[0008] In one aspect, the invention features a strain relief system
for restraining a lead relative to a housing. The strain relief
system includes a positive axial restraint component for
restraining axial movement of the lead relative to the housing and
a positive rotational restraint component for restraining
rotational movement of the lead relative to the housing. The
positive axial restraint component and the positive rotational
restraint component are independent components arranged in a spaced
relationship relative to each other. In one embodiment, the
positive axial restraint component comprises a quick disconnect
connector and the positive rotational restraint component comprises
a shaped boot attached to the lead.
[0009] In another aspect, the invention features a plasma arc torch
for piercing or cutting a workpiece. The plasma arc torch includes
a torch body, a power supply, a lead with two ends. The first end
of the lead is connected to the torch body, and the second end of
the lead is attached to a strain relief system to couple the lead
to the power supply. The strain relief system includes a positive
axial restraint component for restraining axial movement of the
lead relative to the power supply and a positive rotational
restraint component for restraining rotational movement of the lead
relative to the power supply. The positive axial restraint
component and the positive rotational restraint component are
independent components arranged in a spaced relationship relative
to each other.
[0010] In another aspect, the invention features a method for
restraining a lead relative to a housing. The method includes the
steps of providing a positive axial restraint component for
restraining axial movement of the lead relative to the housing, and
providing a positive rotational restraint for restraining
rotational movement of the lead relative to the housing, and
connecting the lead to the housing. The positive axial restraint
component and the positive rotational restraint component are
independent components arranged in a spaced relationship relative
to each other.
[0011] In yet another aspect, the invention features a method for
restraining a lead relative to a power supply for a plasma arc
torch. The method includes the steps of providing a positive axial
restraint component for restraining axial movement of the lead
relative to the power supply and providing a positive rotational
restraint component for restraining rotational movement of the lead
relative to the power supply. The positive axial restraint
component and the positive rotational restraint component are
independent components. The method also includes the step of
arranging the positive axial restraint component and the positive
rotational restraint component in a spaced relationship relative to
each other along a longitudinal axis of the lead. Further, the
method includes the step of connecting the lead to the power supply
for the plasma arc torch.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagram of a strain relief system used to
connect a lead to a housing.
[0013] FIG. 2 is a diagram of a plasma arc torch power supply, lead
and a torch body used for cutting or piercing a metal
workpiece.
[0014] FIG. 3 is a schematic cross-sectional view of a conventional
plasma arc torch.
[0015] FIG. 4 is a cross-section view of the lead from FIG. 2.
[0016] FIG. 5 is a diagram of a lead, shaped boot, and quick
disconnect connector.
[0017] FIG. 6 is a diagram of a lead attached to a plasma arc torch
power supply.
[0018] FIG. 7 is a cross-section along a longitudinal axis of the
lead attached to the plasma arc torch power supply from FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0019] FIG. 1 illustrates a strain relief system which connects a
lead to a housing. The strain relief system 10 prevents axial
movement and rotational displacement of the lead 12 relative to the
housing 14. The strain relief system 10 includes a positive axial
restraint component 16 for restraining axial movement of the lead
12 relative to the housing 14 and a positive rotational restraint
component 18 for restraining rotational movement of the lead 12
relative to the housing 14. The positive axial restraint component
16 and the positive rotational restraint component 18 are
independent components arranged in a spaced relationship relative
to each other.
[0020] In one embodiment, the positive axial restraint component 16
can include a quick disconnect connector 22 attached to the lead
12. In another embodiment, the positive axial restraint component
16 can include the quick disconnect connector 22 and a quick
disconnect connector receptacle 17 positioned inside the housing
14.
[0021] In one embodiment, the positive rotational restraint
component 18 can include a shaped boot 24 attached to the lead 12.
In another embodiment, the positive rotational restraint component
18 can include the shaped boot 24 and a mating receptacle 28 formed
in the housing 14. The shaped boot 24 and the mating receptacle 28
are designed to prevent rotation of the lead 12 when the shaped
boot 24 is inserted in the mating receptacle 28. The shaped boot 24
and mating receptacle 28 are designed to have anti-rotation
features 25a, 25b, 25a', and 25b' to prevent rotation of the lead
12 relative to the housing 14.
[0022] The positive axial restraint component 16 and the positive
rotational restraint component 18 are arranged in a spaced
relationship relative to a longitudinal axis 20 of the lead 12. In
addition, the positive axial restraint component 16 and the
positive rotational restraint component 18 can be configured so
that both are engaged simultaneously when the lead 12 is connected
to the housing 14.
[0023] Generally, the strain relief system 10 can be useful in a
variety of tools. However, it has been found that the strain relief
system described herein is particularly useful in a plasma arc
torch system.
[0024] FIG. 2 illustrates a plasma arc torch system representative
of any of a variety of models of torch systems. A power supply 60
provides continuously variable current output within a range (e.g.
from about 20 to 40 amperes). This range can be lower or higher
depending on the torch system, the thickness the workpiece and the
desired cutting speeds. The variable power supply allows for wide
variations in cutting speeds for a given thickness of metal.
[0025] A torch body 62 configured for hand cutting is connected to
the power supply 60 by a lead 12. The power supply 60 is enclosed
by housing 14. The lead 12 is connected to the power supply 60 by a
strain relief system 15. The lead 12 provides the torch body 62
with a plasma gas from a gas source (not shown) and electrical
power from the power supply 60 to ignite and sustain a plasma
stream. In one embodiment, air is used as the plasma gas, but other
gases can be used to improve cut quality on metals such as
stainless steel and aluminum. A workpiece lead 66 provides a return
path for the current generated by the power supply 60 and is
typically connected to a workpiece (not shown) by a clamp 68.
[0026] FIG. 3 illustrates in simplified schematic form a plasma arc
torch representative of any of a variety of models of torches. The
torch has a body 70 which is generally cylindrical with an exit
orifice 72 at a lower end 74. A plasma arc 76, i.e. an ionized gas
jet, passes through the exit orifice 72. The torch is used to
pierce and cut metal, such as mild steel or other
electrically-conducting materials, in a transferred arc mode. In
cutting mild steel, the torch operates with a reactive gas, such as
oxygen or air, or a non-reactive gas, such as nitrogen or argon, as
the plasma gas to form the transferred plasma arc.
[0027] The torch body 70 supports an electrode 89 having an insert
88 in its lower end and a nozzle 78 spaced from the electrode 89.
The nozzle 78 has a central orifice that defines the exit orifice
72. A swirl ring 80 is mounted to the torch body 70. In one
embodiment, the swirl ring 80 has a set of radially offset (or
canted) gas distribution holes 82 that impart a tangential velocity
component to the plasma gas flow causing it to swirl. This swirl
creates a vortex that constricts the arc and stabilizes the
position of the arc on the insert.
[0028] In operation, the plasma gas flows through a gas inlet tube
84 and the gas distribution holes 82. The gas flows into the plasma
chamber 86 and out of the torch through the exit orifice 72. A
pilot arc, which ionizes the gas passing through the exit orifice,
is first generated between the electrode 88 and the nozzle 78. The
arc then transfers from the nozzle to a workpiece 90. It is noted
that the particular construction details of the torch body,
including the arrangement of components directing of gas and
cooling fluid flows and providing electrical connects, can take a
wide variety of forms.
[0029] When repairing or replacing the torch head 74 or lead 12, it
is important that the lead connected between the torch and the
power supply can be disconnected from the power supply. In
addition, operators often wish to disconnect the torch from the
power supply for convenience during storage or transport of the
system.
[0030] FIG. 4 illustrates a cross-section of the lead 12 (Section
A-A from FIG. 2) used to supply current and gas to the torch body
62. The lead 12 has wires 30 for delivery of current from the power
supply 60 to the torch body 62. In addition, a hose 32 delivers gas
from the power supply to the torch body. In one embodiment, the
hose 32 is centrally located within the lead 12. In another
embodiment, the hose 32 is not located in the center of lead 12. In
still another embodiment, there can be more than one hose 32 in
lead 12. The wires 30 and hose 32 are located inside of a jacket
34. Fillers 36 are disposed in remaining spaces inside the jacket
34 to provide support and fill in empty space.
[0031] FIG. 5 illustrates the lead 12 and the shaped boot 24. The
lead 12 also includes a quick disconnect connector 22. The quick
disconnect connector 22 can be connected to the quick disconnect
connector receptacle 17, which in one embodiment is secured within
the housing 14 (FIG. 1) of the power supply 60. The quick
disconnect connector 22 also functions as a gas fitting to allow
gas or fluid to be transferred from the power supply 60 to the
torch body 62 via lead 12. Wires 30 can extend through holes 38 to
connect the wires 30 with an electrical connector in the power
supply 60 (FIG. 6).
[0032] FIG. 6 illustrates the portion of the lead 12 connected to
the power supply 60. The lead 12 has a longitudinal axis 20. The
lead further includes the shaped boot 24 molded over the jacket 34.
The mating receptacle 28 and shaped boot 24 are both compatibly
shaped to allow the shaped boot 24 to fit securely within the
mating receptacle 28 and have anti-rotation features 25a, 25b, 25a'
and 25b' to prevent rotation of the lead 12 relative to the housing
14.
[0033] As shown in FIG. 6, the lead 12 is connected to the quick
disconnect connector receptacle 17 located in the housing 14 of
power supply 60. FIG. 7 is a cross-section (Section B-B from FIG.
6) taken perpendicular to the longitudinal axis 20 of lead 12 and
illustrates the connection of lead 12 to the quick disconnect
connector receptacle 17. The embodiment shown uses the quick
disconnect connector receptacle 17, which engages the quick
disconnect connector 22. The quick disconnect connector 22 also
acts as gas fitting, allowing gas or fluid to be supplied with the
lead 12 from the power supply to the torch body 62. The foregoing
are merely representative embodiments, as other configurations are
possible and within the scope of the inventions.
[0034] Equivalents
[0035] While the invention has been particularly shown and
described with reference to specific preferred embodiments, it
should be understood by those skilled in the art that various
changes in form and detail may be made therein without departing
from the spirit and scope of the invention as defined by the
appended claims.
* * * * *